1. Field of the Invention
This invention relates to a magnetic head for use in magnetic recording and to a fabrication method thereof. An embodiment of the present invention relates particularly to a read/write magnetic head which is suitable for high density read/write operations.
2. Description of the Prior Art
A conventional magnetic head technology is disclosed in JP-A-59-178609, for example.
A magnetic head of the type in which only a head gap portion projects to a medium direction has been proposed in order to accomplish high density recording in magnetic recording. For example, xe2x80x9cIEEE TRANSACTION ON MAGNETICSxe2x80x9d, Vol. 24, No. 6, November, 1984, pp. 2841-2843, describes a method of deciding a track width of a magnetic head by applying machining from an air bearing surface side.
As to a magnetoresistive head (hereinafter referred to as the xe2x80x9cMR headxe2x80x9d) used as a read-only magnetic head, too, JP-A-59-71124 and JP-A-1-277313 disclose the structure in which only a track width portion (magnetic sensing region) is projected to a medium opposing surface.
On the other hand, a read/write magnetic head produced by integrating the MR head and an induction type write head is known from JP-A-51-44917, and so forth.
However, the magnetic head having the structure of the IEEE reference described above involves the problem that off-track performance is low because a flux leaks from regions other than the track width which is defined by etching. Since a relatively wide region of a slider rail is removed by etching, floating characteristics of a slider vary greatly before and after machining. If etching technique used for an ordinary semiconductor process is utilized, it becomes extremely difficult to coat uniformly a resist onto the slider rail, and the problem of mass-producibility is left unsolved.
The technology disclosed in JP-A-59-71124 and JP-A-1-277313 is not free from the following problem. When the MR head only the magnetic sensing region of which is allowed to project is produced, magnetic shield layers that interpose the MR sensor between them from both sides are greater than the width of projection, so that flux from adjacent tracks which cross one another through these shield layers results in noise. This invites the problem that a signal-to-noise ratio drops when signals become weaker with a smaller track width.
Furthermore, when a composite magnetic head is produced by combining the MR sensor only the magnetic sensitive region of which projects and the induction type write head, the width of the write magnetic pole and that of the projecting portion of the MR sensor deviate from each other due to a positioning error and the ratio of this deviation to the track width becomes greater with a smaller track width. Therefore, another problem occurs that read efficiency drops. In other words, the conventional MR head described above employs the structure wherein only the track width portion is projected to the medium opposing surface so as not to detect signals at portions other than at the read track width for the purpose of accomplishing a smaller track width. In the conventional head of this kind an MR sensor pattern only the track width portion which projects is formed on a substrate and a read head and the like are formed in such a manner as to align with this projecting portion. Thereafter the substrate is cut and the cut surface is polished in order to obtain a head only whose projecting portion is exposed to a medium opposing surface. Accordingly, the projecting width of the MR sensor and the width of shield layers and the width of the recording magnetic pole and the projecting with the MR sensor do not inevitably coincide with one another, respectively.
It is a first object of the present invention to provide a narrow track magnetic head having excellent off-track performance and a fabrication method thereof.
It is a second object of the present invention to provide a magnetic head having a high signal-to-noise ratio.
It is a third object of the present invention to provide a read/write magnetic head free from a positioning error between a write head and a read head but having a high signal-to-noise ratio.
It is a fourth object of the present invention to provide a fabrication method of a magnetic head which reduces the track width of a magnetic head without changing floating characteristics of a slider.
It is a fifth object of the present invention to provide a fabrication method of a magnetic head for high density recording having a narrow track width at a high fabrication yield.
The first object of the-present invention described above can be accomplished by disposing at least one trench or groove at part of an air bearing surface between a magnetic head and a medium. More definitely, local recesses are defined near a magnetic gap of the magnetic head or its magnetic sensing region so as to define the width of these members. In one preferred embodiment of the invention, these trenches or recesses are formed by focused ion beam (hereinafter referred to as xe2x80x9cFIBxe2x80x9d) machining. In another preferred embodiment of the invention, a material is packed into these trenches or recesses.
The second object of the invention described above can be accomplished by carrying out track width machining as a bulk from an air bearing surface side after an MR sensor and shield layers are formed on a substrate.
The third object of the invention described above can be accomplished by forming a write head and a read head on a substrate and then carrying out track width machining by etching from a polished and cut surface in order to prevent the track position error between the write head and the read head. In other words, while only the track width portion of a soft magnetic film of each of the write and read heads constituting the magnetic head is left on a floating surface, the other portions are removed in such a manner as to increase the distance from the medium. At the same time, track width machining is applied also to the shield layer of the read head so that only the projecting portion is exposed on the floating surface. In still another preferred embodiment of the present invention, a stopper material for etching is disposed in advance on a machining portion in a head lamination process in order to prevent the exposure of a planarization layer that covers the coil of the write head and a coil when machining is made from the floating surface.
The fourth object of the invention described above can be accomplished by machining part of a rail of an air bearing surface of a head slider by use of a focused ion beam.
The fifth object of the invention described above can be accomplished by machining the shape of the magnetic head by use of a beam having focused energy without coating a resist onto the slider rail.
When at least one trench is disposed at part of the air bearing surface of the magnetic head with the medium, a magnetic flux does not leak from regions other than from the track width region defined by the trench. Accordingly, a narrow track magnetic head having high off-track performance can be provided.
Yield and accuracy of machining can be improved by using a focused ion beam when the trench is formed only at part of the air bearing surface.
The leak of the flux can be reduced further by packing a material into the trench described above.
After the MR sensor and the shield layer are formed on the substrate, track width machining is carried out as a whole from the air bearing surface side with respect to the medium and in this manner, the width of the shield layer can be made substantially equal to the projecting width of the MR sensor. Accordingly, the flux from adjacent tracks does not mix through the shield layer, resulting in no noise, so that a magnetic head having a high signal-to-noise ratio can be obtained.
In the present invention, the distance between the members inclusive of the magnetic shield layer and the medium and between the magnetoresistive sensor and the medium, that is, the spacing, is great at the portions other than the projecting portion which functions as the magnetic sensing region. Accordingly, the signals from the portions other than the magnetic sensing region can be reduced remarkably. When a floating distance is 0.15 xcexcm and a move-back distance is 2 xcexcm, for example, a signal from adjacent tracks can be reduced by at least xe2x88x9250 dB with respect to a signal at a recording wavelength of 2 xcexcm. Since the portions other than the magnetic sensing region are thus moved back, the noise resulting from-the adjacent tracks can be reduced drastically.
Positioning of the track width between the write head and the read head can be made extremely precisely by carrying out track width machining of both of the heads simultaneously and as a bulk. If an etching stopper is used, an etching margin can be increased even when FIB is not used.
If the projecting portion is formed by utilizing focused ion beam etching (FIB) or if a method which defines a trench at part of the slider rail of the head is employed, a trench having a large aspect ratio can be formed in a very small region. Consequently, machining does not exert adverse influences on the floating characteristics of the slider.
If the shape of the magnetic head is machined by a beam having focused energy without coating a resist onto the slider rail, a desired shape can be machined at a high yield. Furthermore, since an electrically conductive layer can be formed inside the trench thus formed, a magnetic shield material can be packed easily into the trench by field plating or the like, and a head having high off-track performance can be fabricated.